I have a home made PS that has a problem. It is a variable PS that I have been using for several years. It suddenly developed a problem I can't figure out. The schematic is attached, but doesn't show the transformer, rectifiers, and capacitors, since that portion works fine.
I have verified all resistors are ok and all transistors and the diode check ok with an analog ohmmeter. The LM317 is in the TO-220 package and has a heat sink on it.
The PS powers on and the voltage is adjustable. It will power a 200 ohm load with no problem, but, as the resistance is decreased, the voltage drops until it finally reaches zero. If I remove the two 2N3055 transistors, it does the same thing. I suppose that means the LM317 is bad. I don't currently have another to try replacing it.
Suggestions?
Correction to schematic. It's not a 2N2905, it's an MJE104. Shouldn't matter.
I have verified all resistors are ok and all transistors and the diode check ok with an analog ohmmeter. The LM317 is in the TO-220 package and has a heat sink on it.
The PS powers on and the voltage is adjustable. It will power a 200 ohm load with no problem, but, as the resistance is decreased, the voltage drops until it finally reaches zero. If I remove the two 2N3055 transistors, it does the same thing. I suppose that means the LM317 is bad. I don't currently have another to try replacing it.
Suggestions?
Correction to schematic. It's not a 2N2905, it's an MJE104. Shouldn't matter.
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